Both steady and pulsatile flow through simulated, rigid and flexible vascular stones will be studied in order to compare the pertinent flow characteristics to the geometry and flexibility of the stenoses. As a starting point, velocity profiles will be measured by photographing small particles flowing in glycerine-water solutions in rigid plexiglas tubes containing stenoses of known geometry. Pressures at the walls will be monitored, and the nature and extent of the separated regions of flow in the diverging sections of the stenoses will be measured. The results will be compared with a theoretical solution in order to assess the merits of the experimental techniques. Whole blood will then be used, and the pressures and separated regions determined and compared to those of the transparent fluid. Regions of relatively high and low pressures and wall shearing stresses will be located. Flexible models will be constructed to some of the same geometries as the rigid tubes and experimental results obtained will be compared to the previous cases. Finally, flow through mammalian arterial and/or venous segments will be studied and the results related to the previous studies mentioned. This investigation will help to determine under what flow conditions a Newtonian, transparent fluid behaves essentially as blood, and under what circumstances a rigid and/or flexible model of a vascular lesion with a transparent fluid or blood flowing through it makes a good model of the flow of blood through a diseased artery. The study will also provide some new insights into the role of fluid mechanics in vascular disease.